| Two sets of reciprocal introgressive line population (IL) were developed by 2-4x backcross and more than 2x selfmg from a cross between elite japonica rice variety "Lemont" from US and indica variety "Teqing".Total 494 lines were used in this study, including 217 ILs with Lemont background (denoted as Lemont population hereafter), 275 ILs with Teqing background (Teqing population), and their 2 parents.Field experiment was carried out in 2000 using a randomized block design having 3 replications. Single plot had 5 lines with 7 plants each line. Total 20 traits were observed or measured, including days from sowing to heading (DSH), plant height (PLH), flag leaf length and width (FLL, FLW), last second leaf length and width (SLL, SLW), tiller angle (TLA), flag leaf angle (FLA), 1st elongated internode length and stem diameter (INL, STD), panicle number per plant (PNN), panicle length (PNL), primary branch number per panicle (PBN), second branch number (SBN), ratio of second and primary branch number (SPR), spikelet number per panicle (SNP), spikelet density (SPD), fertility percentage (FRP), hundred grain weight (HGW) and grain weight per plant (GWP, average of 8 individuals).Following the order and distance of a linkage map developed from a set of RI population from the same cross, 139 and 147 markers were used in this study to build linkage maps and detect genotypes in Lemont and Teqing population respectively, including 110 SSLPs, 26 RAPDs (for Lemont population) or 33 RAPDs (for Teqing population), and 3 morphological markers.Data analysis were conducted in several steps, including frequency distribution and ANOVA (SPSS for Windows V10.0), graphic genotyping (MapPlotter V2.0), introgressive allele and segment search, whole genome introgression overlapping map, significant marker search by oneway ANOVA and mean comparison (SPSS for Windows V10.0), and interval mapping or multiple interval mapping (MapManager QTX Vbl3).The results show trend of regression of ILs to recurrent parent while there are wide variance for each traits. There are 3 styles of frequency distributions according the degree of overlapping between reciprocal ILs. High significance (P0.001) were observed between lines for all traits and between blocks for some traits in both IL populations.Depending on the number of introgressive alleles per line, there are 9.02% homozygous Teqing genotypes, 3.81% heterozygous loci in ILs with Lemont background. Total introgressive content (P2+H/2) was as high as 10.95%. The percentage of introgressive homozygotes, heterozygote and all Lemont alleles are 7.97%, 3.18%, and 9.56% in Teqing IL population respectively. Counted as line numbers with different genotypes at each locus, percentage of Teqing allele varied from 1.15% (OSR20 on chr 12) to 47.36% (RM234 on chr 7), having a mean percentage of 11.1% in Lemont ILpopulation. In Teqing IL population, the lowest introgressive loci was RM219 (2.72%) on chr 9, while the highest was Q050500 (24.19%) on chr 4. There are average 9.96% of lines having Lemont allele at each locus. The proportion of introgressive alleles is different for chromosomes. The range varies from 8.60% for chr 1 to 22.81% for chr 7 in Lemont population and from 7.11% for chr 7 to 12.90% for chr 4 in Teqing population. The introgressive ratio also varied along chromosomes, while there are opposite magnitude in some chromosomal regions. It was unpredictable that there is higher portion of introgressive alleles at the end of chromosomes.There are total 2128 introgressive segments in Lemont IL population, meaning 9.81 segments for each line including 4.37 homozygous segments covering only 1 marker locus, 2.22 homozygous segment covering more than 2 loci, 2.18 heterozygous segment covering single locus, 0.56 heterozygous segments covering more than 2 loci, and 1.37 segment covering both homozygous and heterozygous loci. Total length of introgressive segments was 246.0cM on the average, varying from 1.3cM to 664.6cM. The average length of introgressive segments accounts for 11.22% of whole l... |
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